I am confused. You previously posted that you want to market your pies commercially, but you don't even make your own crust? I would learn how pretty quickly if you really do want to sell them. You cannot sell products as your own if they have store bought crusts.

If you want to use store bought crust but cant find the right size, maybe you could buy the regular size and re roll it into two smaller circles and see if they fit. An 8-9 inch pie crust should theoretically make two 4-inch ones.